This invention relates to a composite laminate or bonded laminated structure and to a method of making such laminate. More specifically this invention relates to a highly flexible composite laminate of a relatively light to medium gauge or thickness comprised of a hot melt type thermoplastic material and a textile woven fabric material. This invention even more particularly relates to a laminate of a polyethylene thermoplastic material and a textile fabric material comprised of polyester or a combination of polyester and nylon useful for example, as a conveyor belt or the like.
It is known in the art to form laminates of thermoplastic material and textile woven fabric material for use in products such as conveyor belting and other web-like structures. For example, my co-pending application Ser. No. 525,786 entitled, "Textile Composite Structure and Method of Preparation" filed Nov. 21, 1974, now U.S. Pat. No. 3,962,511 relates to a textile fabric composite such as an industrial belt. The belt is prepared by encapsulating the fibers of the fabric with a polyurethane reaction mixture, drying and at least partially curing the reaction mixture, adhering an overlayer of a flexible thermoplastic to one surface of the encapsulated fabric and pressing the thermoplastic into the interstices of the encapsulated fabric under pressure and with the application of heat. This type laminated structure has been found to be highly satisfactory for use as a heavy duty conveyor belt for example, as used in the handling of abrasive materials such as metal parts, ore or coal. However, this structure is not appropriate for light to medium gauge laminates for example, in the range of from about 0.076 mm to about 0.370 mm (0.030 to 0.145 inches) wherein a high degree of flexibility is desired.
Satisfactory laminates of thermoplastic material and particularly polyethylene type thermoplastic material have been difficult to produce and have been relatively inflexible due to the methods heretofore used for producing such laminates. These methods have generally involved the fabric being totally impregnated with the thermoplastic material by completely filling all the interstices in the fabric as disclosed in U.S. Pat. No. 2,824,034 to Worby entitled, "Methods of Impregnating A Fabric With Polyethylene". Laminated structures in which there is a total penetration of the thermoplastic material into the interstices or voids of the fabric and even in some instances into the yarn structure itself results in a relatively stiff or boardy product having insufficient flexibility. Therefore when such structures are used to produce conveyor belting often flex-cracking occurs after only a limited period of use.
Furthermore, heretofore, if it was desired to have one face or surface of the fabric free of thermoplastic material conventional techniques could not be used since the complete penetration of the fabric interstices by the thermoplastic material resulted in a "strike through" effect with the thermoplastic material being present on each opposite face of the fabric.
It has been found that the disadvantages of the prior art can be overcome by the present invention which will be hereinafter described.